It is commonly reported that swimmers store greater amounts of body fat than runners. Male swimmers (N = 8), male runners (N = 8), and male triathletes (N = 6) were compared for the source of energy (substrate use) for equivalent levels of exercise oxygen consumption and during two hours of recovery.

It was found that during the two activities at the same level of intensity substrate use (energy used) was significantly different. Swimmers used more carbohydrate for energy than runners. Swimmers also recorded significantly higher lactate levels after exercise. However, during recovery there were no differences between the activities in terms of fat storage. These results did not support the hypothesis of increased fat storage in swimmers.

Implication. The source energy used by swimmers is different to that of runners when effort levels are equated. This suggests that the muscle fibers that propel each activity are different. However, this difference was not reflected in recovery physiology and so the role of fat storage, particular in swimming, is not clarified by this investigation.